But these indicate that of the two, he was on the ballot only in Missouri, not in Oklahoma. Actually, On the campaign trail, March 2012says he wasn't on the ballot in Oklahoma.

I also had a bit of trouble verifying unambiguously that he was the only challenger in Arkansas; I did a sanity check on that with The Green Papers, but don't feel any need to list it under article Sources.

(Ah, I see that one's mentioned in one of the interview questions.)

I'm almost completely failing to verify the key background sentence at the start of the fourth paragraph (starting with his being a lifelong Democrat). One more thing to try, and then failing that I'll pull almost all of the sentence (ouch), and publish.